You should never use radeonfb, *never*. If you want to use the open source radeon driver, activate KMS in the kernel. This way efifb will load first, and shorty after radeon KMS (radeondrmfb) will take over. If you want to use the closed source fglrx driver, do *not* have anything radeon related in the kernel, just efifb.

According to Linux Kernel Documentation :: fb : efifb.txt, Efifb only support Intel based Apple computers. So on PC comptibles it is useless. Use Radeon KMS as framebuffer with free Radeon Xorg drivers and Vesafb or Uvesafb with proprietary Ati/Amd drivers. Only one framebuffer device s needed. You advoid possibles conflicts.

The Radeonfb framebuffer driver never work for me so the 'DDC/I2C for ATI Radeon support' is just a trap. You have a kernel command line radeon.hw_i2c=1 to support I2C bus with the Radeondrmfb framebuffer.

If you are not able to add the good firmware for your card directly in the kernel if Radeon KMS is compiled in, or in the initramfs if Radeon KMS is compiled in module, check the kernel messages after boot, at least via Ssh if not possible otherwise. The Drm support will tell which firmware files are missing. You can ask (the search engine) if needed.